Closed system recirculating assembly



United States 3,388,866 CLOSED SYSTEM RECIRCULATING ASSEMBLY Gustave S.Levey, Houston, Tex., assigner to rlhe Spec- Flo ManufacturingCorporation, Houston, Tex., a corporation of Texas Filed Jan. 15, 1965,Ser. No. 425,808

7 Claims. (Cl. Z39- 127) This invention relates generally to liquiddistribution systems and more particularly t-o a novel and improvedrecirculating pressure system for airless paint spraying devices and thelike.

The present invention is directed to a recirculating system for paintspraying and the like, arranged to maintain a relatively high pressurein the paint at the spray gun normally in the order of tive hundredpounds per square inch to th-ree thousand pounds per square inch.

In order to maintain the desired pressure at the spray gun a systemaccording to the present invention includes an adjustable back-pressurerelief valve which remains closed unless the pressure in the return lineand in turn at the spray gun is equal to the adjusted pressure and thenopens to modulate the recirculating iiow, thus maintaining desiredpressure. The system pump is provided with suiicient capacity to atleast supply the maximum amount of paint required by the spray gun orguns at a pressure at least equal to the desired or adjusted pressure ofthe back-pressure relief valve. Normally the pump is selected to haveexcess capacity so that continuous recirculation is provided.

A heater is provided in the supply line from the pump to the spray gunwhich because of the recirculating flow maintains a uniform painttemperature even when the spray gun is intermittently operated. Therelief valve is adjustable so that the user can select the correctoperating pressure for the particular painting conditions and paintbeing used.

The adjustable back-pressure relief valve includes a valve elementresiliently urged toward a seat by a spring, the compression of which ismanually changed by turning an adjusting screw. A seal of the O-ringtype seals against the adjusting screw preventing leakage. In order tomaintain a positive pressure -on the seal to insure proper sealing, afixed back-pressure relief valve is provided in the circuit downstreamfr-om the adjustable back-pressure relief valve. This xed relief valveis totally enclosed and requires no external dynamic seals so leakagedoes not occur therein. It performs the dual function of preventing airfrom entering the pressure system when the system is initiallypressurized and also maintains a positive pressure on the seal aroundthe adjusting screw insuring proper sealing thereof during operation.

It is an important object of this invention to provide a novel andimproved pressurized liquid recirculating system including adjustableback-pressure relief valve means and xed back-pressure relief valvemeans arranged to prevent air pollution of the system and leakage.

It is another important object of this invention to provide arecirculating pressure system for paint spraying and the like combininga pump, an adjustable back-pressure relief valve and separate pressuremeans for maintaining the discharge of the relief valve at a minimumpressure.

It is another important object of this invention to provide a novel andimproved back-pressure system for recirculating pressure systemsincluding an adjustable backpressure relief valve operable t-o preventrecirculating flow at pressures below an adjusted pressure incombination with a xed pressure back-pressure relief valve operable tomaintain a minimum back-pressure in the adjustable valve.

3,385,866 Patented June 18, 1958 It is another important object of thisinvention to provide a novel and improved recirculating system forairless spray guns and the like, including a pump operable to provide anexcess of liquid paint at operating pressures, an adjustableback-pressure relief valve operable to maintain adjusted operatingpressures during normal operation, and a fixed back-pressure reliefValve operable to prevent discharge from the adjustable back-pressurerelief valve at pressures below a minimum pressure.

It is still another object of this invention Ito provide a recirculatingpressure system according to the last preceding lobject including heatermeans for controlling the temperature of the recirculating paint.

Further objects and advantages will appear from the followingdescription and drawings wherein:

FIGURE 1 is a schematic illustration of the recirculating pressuresystem incorporating this invention; and

FIGURE 2 is an enlarged fragmentary view partially in sectionillustrating the structure of the back-pressure relief valve.

FIGURE 1 illustrates an embodiment of this invention utilizing a pump 10operable to draw paint up an inlet line 15 from a paint container ordrum |11. The pump illustrated is driven by a reciprocating air motor 12and operates to supply paint under pressure to an outlet 13. Theparticular structure of the pump and its drive is disclosed in detail inmy U.S. Patent No. 3,018,968. The particular pump structure is notcritical to this invention except insofar as it cooperates with theremaining portions of the systems and it is merely necessary that thepump be operable to continuously provide a ow rate at least as great asthat required for the operation of the spray gun at the requiredoperating pressures of the spray gun.

The outlet 13 of the pump 10 is connected by a pres- 'sure line 14 to aheater 16 and from the heater 16 through a pressure line 17 t-o a spraygun 18. The spray gun 18 may be of any suitable type and reference maybe made to my U.S. Patent No. 3,000,576, granted Sept. 19, 1961, for adetailed description of a preferred form of spray gun which may be usedwith a system incorporating this invention.

A return line 19 connects the spray gun 1S to a backpressure reliefassembly 21 which discharges to the intake 23 of the pump 10.Preferably, the intake 23 is of the type which prevents mixing of therecirculated paint with the paint in the container 11 so that only thepaint being pumped out of the container is heated.

The pump 10 operates to deliver paint at operating pressure with avolume at least equal to the volume Iof paint sprayed by the vspray gun18 when the gun is operated. It should be understood that if desiredmore than one spray gun 18 may be connected to the pressure lines 17Aand 19. In such installations the pump must have suflicient capacityfor the combined operation -of the spray guns. The back-pressure reliefvalve assembly 21 in combination with the pump functions as a pressureregulator maintaining a pressure `at the spray gun equal to theoperating pressure set by the adjustment of the 'back-pressure reliefvalve assembly.

Referring now to lFIGURE 2, the back-pressure relief valve lassembly 21includes a main body 26 formed with an inlet chamber 27 and `au outletpassage 2S. The `upper end of the body 26 is formed with -a threadedopening 29 aligned with a bore 31 connecting the inlet chamber 27 andthe 'outlet passage 28. An inlet port 32 is threaded to receive afitting 33 connected through a T 34 4to the return line 19. Therefore,the recirculating flow through the return line is connected to the inletchamber 27. A pressure gauge 36 is mounted on the T 34 adjacent to theback-pressure relief valve assembly so that the user can determine theoperating pressure. A bleed port 37,

also open to the inlet chamber 27, is threaded to receive a bleed valve38 which in turn is provided with a bleed hose 39.

A regulating valve assembly 41 includes fa v-alve body 42 threaded intothe opening 29 and provided with 1a valve section 43 positioned Withinthe bore 31. A seal 44 prevents leakage therebetween. A valve seatelement 46 is mounted in the valve section 43 and pressed against a seal42S by .a threaded ring 47. A tubular Astern support i9 is threaded intothe v-alve body 42 and is internally threaded adjacent to its outer endto receive the adjusting stern 51. An `O-ring 52, preferably formed ofTeflon, provides a seal between the adjusting stem 51 and the inner wallof the stem support 49.

A ball valve 53 is carried by ka valve stem 54 which extends into 1andis guided by the Walls of an axial bore in the yadjusting stem 51. -Aspring 56 extends between a thrust member 57 seated against the end faceof the adjustable stem 51 and the valve stem 54 resiliently urging thevalve stem fand in turn the ball valve 53 ltoward 4the valve seat with aresilient force which is the function of the adjusted position of theadjusting stem. Therefore, the pressure in the inlet kchamber 27required to lift the ball valve 53 away from the seat 46 to allow flowthrough the device is a function of the adjusted position of the stem51. If higher pressures are required the stem is rotated in ra clockwisedirection to screw it down into the body Iand if lower pressures arerequired anticlockwise rotation of the stem 51 causes it to reduce thespring force. Seals 55 and 55a are provided between the stern support49, the valve body 42, and the body 26 of the assembly.

In order to insure that 4a minimum back-pressure is provided in theoutlet passage 27 a fixed relief valve `assembly 58 is threaded into Ianoutlet opening 59. The assembly S includes a body 61 having a valve seat'62. A swivel nut 63 is mounted on the body 61 and threads onto a swivelfitting 64 mounted on the intake 23. A spring 66 extends between -ashoulder on the swivel fitting 64 and a ball valve 67 resiliently`urging the ball valve against the seat 62. Preferably, the elements ofthe fixed relief valve assembly are proportioned so thaty a pressure inthe outlet passage 28 is in the order of twenty-five pounds per squareinch before `the ball valve 67 `is lifted off of the seat 62 to allowflow. Therefore, the fixed relief valve Iassembly maintains a minimumpressure in the order of twenty-five pounds per square inch on the lowpressure side of the adjustable relief valve t1 thereby maintaining apositive pressure on the seal 52 to insure its proper operation. Also,when the system is first pressurized lair in the system is not permittedto flow into the system from the relief valve, even when vacuums occur.

In operation the pump is started with the bleed valve 38 open to permitthe air to escape from the system as the paint flows through the linesto `the spray gun 18 and back to the relief valve. When all of the airis out of the lines and any required flushing is completed the bleedvalve 38 is closed yand continued pumping causes the pressure in thelines, the Igun and the inlet chamber 27 to build up to a pressuredetermined by the setting of the `adjustable stem 51. During thebleeding and normal operation of the system the pump produces a vacuumat the intake 23 since the paint level in the container is below theintake 2-3. During bleeding land initial pumping the valve assembly 58remains closed and the vacuum Iat the intake 23 is not ytransmitted tothe valve :assembly 41.

As soon as operating pressure is reached the ball valve 53 is liftedaway fro-m `the seat and the paint Iecircul-ates through the system withthe pressure in the lines 14, 17 and 19, and in the spray gun 18maintained at operating pressure. The pressure in the outlet passage 28is maintained yat a minimum of Iabout twenty-five pounds per square inchdue to the -action of the ball valve `67.

If the fixed relief assembly 58 were not provided a vacuum would occurin the outlet passage 28. This vacnum or low discharge pressure, whichwould occur in the absence of the fixed pressure relief valve assembly58, would cause working on the seal 52 and would result in leakage.However, back-pressure relief valve 58 prevents the intake vacuum of thepump from being transmitted lto the adjustable relief valve assembly 41Iand leakage at the seal 52 does not occur.

Although a preferred embodiment of this invention is illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted vto without departing from the scope of the invention asdefined in the following claims.

What is claimed is:

1. A liquid pressure system comprising a source of liquid, a pumpoperable to pressurize liquid from said source and deliver it to anoutlet, a liquid dispersing device, a supply pressure line connectingsaid outlet to said dispersing device, and return means connected tosaid dispersing device operating to return excess liquid forrecirculation by said pump, said return means including first reliefvalve means adjustably operable to control operating pressure at saiddispersing device, second relief valve means operable to restrict Howfrom said first relief valve means when the discharge pressure therefromis below a predetermined minimum pressure, and a manually operable bleedvalve in said return means upstream from said second relief valve means.

2. A recirculating pressurized system comprising a source of liquid atsubstantially atmospheric pressure, a pump having an intake connected tosaid source and being operable to deliver liquid under pressure to anoutput, a dispersing device, pressure lines connecting said output tosaid dispersing device and said dispersing device to said intake,adjustable back-pressure means in said pressure lines between saiddispersing device and inlet operable to restrict fiow therethrough whenthe pressure of liquid at said dispersing device is less than apredetermined adjusted presure; said back-pressure means including anexternal control for adjusting the value of said predetermined pressure,and a seal preventing leakage therealong, secondary back-pressure meansin said lines between said adjustable back-pressure means and intakeoperable to restrict flow therethrough when the pressure in saidsecondary back-pressure means is below a minimum pressure, said minimumpressure being above atmospheric pressure and below saidpredeterminedpressure, said secondary back-pressure means being free of externaldynamic seals.

3. A fiow control assembly for use in recirculating paint spray systemscomprising a body formed with an inlet adapted to be connected to arecirculation line, an outlet in said body, a relief valve in said bodypreventing flow between said inlet and outlet when closed andpermittingflow therebetween when open, and adjusting stem threaded intosaid body from the exterior thereof and movable toward and away fromsaid valve, a seal preventing leakage along said adjusting stem, aspring between said releaf valve and said adjusting stem operable tourge said relief valve closed with a force determined by the position ofsaid adjusting stem in said body, pressure in said inlet opening saidrelief valve when the pressure therein reaches a pressure determined bythe position of said adjusting stem relative to said body and a pressureresponsive ow control restricting flow from said outlet at pressuresbelow a predetermined minimum pressure, said pressure responsive flowcontrol being free of external dynamic seals.

4.' A flow controly assembly for use in recrculating paint spray systemscomprising a body formed with an inlet adapted to be connected to arecirculation line, an outlet in said body, a rst relief valve in saidbody preventing ow between said inlet and outlet when closed andpermitting flow therebetween when open, an adjust- U,assess ing stemthreaded into said body from the exterior thereof and movable toward andaway from said first relief valve, a seal preventing leakage along saidadjusting stern, a spring between said first relief valve and saidadjusting stern operable to urge said rst relief valve closed with aforce determined by the position of said adjusting stern in said body,pressure in said inlet opening said first relief valve when the pressuretherein reaches a pressure determined by the position of said adjustingstem relative to said body, and a second relief valve mounted in saidoutlet, said second relief valve including a spring-hiased valve elementrestricting ow from said outlet at pressures below a predeterminedminimum pressure, said second relief valve being free of externaldynamic seals.

5. A ow control assembly for use in recirculating paint spray systemscomprising a body formed with an inlet adapted to be connected to arecirculation line, a bleed valve mounted on said body connected to saidinlet, an outlet in said body, a relief valve in said body preventingflow between said inlet and outlet when closed and permitting flowtherebetween when open, an adjusting stem threaded into said body andmovable toward and away from said valve, a seal preventing leakage alongsaid adjusting stem, a spring between said relief valve and saidadjusting stem operable to urge said relief valve closed with a forcedetermined by the position of said adjusting stern in said body,pressure in said inlet opening said relief valve when the pressuretherein reaches a pressure determined by the position of said adjustingstern relative to said body, and a pressure responsive ow controlmounted in said outlet restricting ilow from said outlet at pressuresbelow a predetermined minimum pressure.

6. A paint spray system comprising a source of paint, a pump operable toproduce a vacuum at its intake to withdraw paint from said source anddeliver paint under pressure to an outlet, a spray gun, a supplypressure line connecting said outlet to said spray gun, and return meansconnected to said spray gun operating to return excess paint to theintake of said pump, said return means including rst relief valve meansadjustably operable to control operating pressure at said gun, secondrelief valve means operable to prevent flow from said rst relief valvemeans when the discharge pressure therefrom is below a predeterminedpressure, and bleed valve means in said system ahead of saidrelieffvalve means, said bleed valve means being operable to an opencondition to bleed air from said system and being closable to seal thepressure side thereof.

7. A flow control assembly as set forth in claim 6 wherein said iirstrelief valve includes an adjusting member extending into said body fromthe exterior thereof and a seal preventing flow along said adjustingmember, and said second relief valve is free of external dynamic seals.

References Cited UNITED STATES PATENTS 152,765 7/1874 Perkes 137-5121,505,331 8/1924 Gold 239-533 1,934,296 11/ 1933 Dorner 239-5702,461,766 2/1949 Peeps` 239-127 2,754,228 7/1956 Bede 239-124 2,729,228l/ 1956 Stevenson 137-199 2,578,334 12/1951 Ashbaugh 137-506 3,000,5679/1961 Levey et al. 239-499 3,018,968 1/1962 Levey et al. 239-127FOREIGN PATENTS 807,165 1/1959 Great Britain.

EVERETT W. KIRBY, Primary Examiner.

1. A LIQUID PRESSURE SYSTEM COMPRISING A SOURCE OF LIQUID, A PUMPOPERABLE TO PRESSURZE LIQUID FROM SAID SOURCE AND DELIVER IT TO ANOUTLET, A LIQUID DISPERSING DEVICE, A SUPPLY PRESSURE LINE CONNECTINGSAID OUTLET TO SAID DISPERSING DEVICE, AND RETURN MEANS CONNECTED TOSAID DISPERSING DEVICE OPERATING TO RETURN EXCESS LIQUID FORRECIRCULATION BY SAID PUMP, SAID RETURN MEANS INCLUDING FIRST RELIEFVALVE MEANS ADJUSTABLY OPERABLE TO CONTROL OPERATING PRESSURE AT SAIDDISPERSING DEVICE, SECOND RELIEF VALVE MEANS OPERABLE TO RESTRICT FLOWFROM SAID FIRST RELIEF VALVE MEANS WHEN THE DISCHARGE PRESSURE THEREFROMIS BELOW A PREDETERMINED MINIMUM PRESSURE, AND A MANUALLY OPERABLE BLEEDVALVE IN SAID RETURN MEANS UPSTREAM FROM SAID SECOND RELIEF VALVE MEANS.